1. Field of the Invention
The present invention relates to a quick die opening technology for facilitating die maintenance or inspection for a press. The technology operates the slide at high speeds and for a slide stroke in the range of from a few millimeters to a slightly more than 10 millimeters.
2. Description of the Related Art
Of various presses used in the industry today, high-speed automatic presses used for stamping, e.g., IC reed frames and connectors, typically operate at a speed (the number of slide strokes) of 1,000 spm or higher, with a slide stroke ranging in a few millimeters to a slightly more than 10 millimeters. The distance between the upper and lower dies (i.e., opening of such a press) is therefore less than 100 millimeters even if the slide is adjusted to its upper limit position with the help of a die height adjustment mechanism. It takes time to move the slide to its upper limit position with the help of the die height adjustment mechanism. When the slide is returned to its original position after the inspection, it is extremely difficult to restore the original slide position, which was established by fine adjustments prior to the inspection. Consequently, die maintenance or inspection procedures have always been difficult and time-consuming. In order to solve this problem, various quick die opening mechanisms have been proposed, wherein die maintenance can be done without removing the dies from the press. For example, Japanese Laid-open Patent Publication H8-112699 discloses a slide device comprising a hydraulic cylinder mechanism between the slide and the small end of the connecting rod, which is connected to the crankshaft. The connecting rod constitutes the piston of the hydraulic cylinder mechanism. A threaded area is formed on the periphery of the cylinder. The threaded area and a worm mechanism together constitute a die height adjustment mechanism. This slide device controls the opening between the upper and lower dies by raising and lowering the slide with the stroke of the hydraulic cylinder.
The problem with the mechanism proposed by the Japanese Laid-open Patent Publication H8-112699 is that the hydraulic cylinder on the slide side increases the slide weight and hence the inertia force generated in the slide vertical strokes. On a high-speed automatic press, wherein the number of slide strokes exceeds 1,000 spm, it is mandatory to reduce the slide weight as much as possible in order to reduce the inertia force of the slide vertical strokes at high speeds. Therefore, it is disadvantageous for a press to be equipped with the mechanism disclosed by the Japanese Laid-open Patent Publication H8-112699 from the standpoint of making the machine to operate at higher speeds. Moreover, it is difficult and hence costly to machine the small end of the connecting rod into a piston-like shape so that it can slide inside the cylinder as well as to machine the inside of the threaded member of the die height adjustment mechanism into a cylinder-like shape, while both which are required in the mechanism disclosed by the Japanese Laid-open Patent Publication H8-112699.
An object of the present invention is to provide a bolster-elevating device that is capable of quickly opening the dies and is suitable for high-speed automatic presses.
According to an embodiment of the present invention, there is provided a bolster-elevating device for a press, which is equipped with a set of dies consisting of an upper die and a lower die, the upper die being affixed to the bottom surface of a slide while the lower die being affixed to the top surface of a bolster, and conducts stamping operations by means of vertical strokes of the slide, wherein the bolster is formed in such a way as to be able to be elevated (raised or lowered) arbitrarily, guide means that guides the vertical strokes of the slide is common with the guide means that guides the elevation (raising and lowering) of the bolster, bolster-elevating drive means that drives the elevating motion of the bolster is provided under the bolster, and the stroke of the bolster-elevating drive means is sufficiently large for providing a wide-enough opening between the upper die from the lower die wide for performing maintenance or inspection of the dies.
One feature of the embodiment is that the guide means for the bolster shares the same element as the guide means for the slide vertical strokes. In other words, the bolster-elevating motions and the slide vertical strokes share the same guide means. Another feature is that the bolster-elevating drive means is provided under the bolster of the press. Another feature is that the stroke (amount of elevation) of the bolster is sufficiently large to provide a wide-enough opening between the upper die from the lower die wide for performing maintenance or inspection of the dies.
According to the bolster-elevating device of such a constitution, there is no need for providing a quick die opening function that provides a wide-enough opening between the upper die from the lower die wide for performing maintenance or inspection of the dies on the slide side. In the prior art mechanism, however, an additional mechanism (hydraulic cylinder, etc.) is used for elevating the slide for securing a specified distance between the upper and lower dies in addition to a conventional drive mechanism (drive mechanism including the crankshaft) for the vertical strokes of the slide, wherein the additional mechanism (hydraulic cylinder, etc.) is provided on the slide side. This causes an increase in the slide weight as well as the inertia force in the slide vertical strokes, consequently causing a hindrance to faster operations of the press. According to the present invention, there is no need to have a mechanism on the slide side for providing the quick die opening function, thus facilitating high-speed operation of the press.
Moreover, since the guide means is shared between the bolster elevation and the slide strokes, the horizontal positioning relation between the slide and the bolster is accurately maintained before and after the die opening for the purpose of die maintenance or inspection. In other words, no misalignment is caused after the die opening for the purpose of die maintenance or inspection, so that there is no need for adjusting the positions of the upper and lower dies again after die maintenance or inspection operations.
According to a second embodiment of the present invention, there is provided a bolster-elevating device for a press according to the first embodiment of the present invention wherein the guide means comprises: pin members extending downward from the bottom surface of the slide and guide members provided on the top surface of the bolster in correspondence with the pin member.
In the second embodiment, the pin members extending downward from the bottom surface of the slide fit guide members on the top surface of the bolster to constitute so-called guideposts, i.e., guide means. Therefore, in addition to the advantage provided by the first embodiment, the second embodiment provides another advantage in preventing misalignment between the upper and the lower dies after die maintenance or inspection operations using a simple structure without recourse to any special guide means.
According to a third embodiment of the present invention, there is provided a bolster-elevating device for a press according to the first or second embodiment of the present invention wherein the bolster-elevating drive means comprises a single or multiple hydraulic cylinder devices.
In the third embodiment, the bolster-elevating device consists of the hydraulic cylinder device(s) so that the press load is borne by hydraulic pressure. In contrast to the third embodiment of the present invention where the press load is borne by hydraulic pressure, the conventional bolster-elevating means, consisting of an electric motor and a rack and pinion mechanism, requires the press load to be borne by the mechanical structural components such as the motor and the rack and pinion mechanism. This makes it necessary for each member to be made larger and sturdier than in the case of the third embodiment of the present invention. Moreover, the constitution of a mechanical structure is generally more complex. Therefore, in addition to the features provided by the first and the second embodiment, the third embodiment provides another advantage of providing a bolster-elevating device of a more simplified and compact structure.
According to a fourth embodiment of the present invention, there is provided a bolster-elevating device for a press according to the third embodiment of the present invention wherein the hydraulic cylinder device comprises: an abutment member on the distal end of a rod affixed to the piston of the hydraulic cylinder device in order to limit the upper limit position of the piston by means of the abutment member.
In the fourth embodiment of the present invention, an abutment member is provided on the distal end of the rod affixed to the piston. This abutment limits the upper limit position of the piston. The conventional die height adjustment device, consisting of a worm mechanism, requires a time-consuming adjustment of the slide position, which consists of turning the worm shaft minutely manually or remotely by a motor controlled by an experienced worker, in order to adjust the slide position after die maintenance or inspection. On the contrary, according to the fourth embodiment of the present invention, the upper limit position of the piston of the hydraulic cylinder device, i.e., the upper limit position of the bolster is controlled by the abutment member. In other words, the bolster position is determined by the position of the abutment member, so that the upper limit position of the bolster does not vary before and after the maintenance or inspection. Therefore, in addition to the advantage according to the third embodiment of the present invention, the fourth embodiment of the present invention provides another advantage of maintaining the parallelism between the slide and the bolster more accurately after the maintenance or inspection as well as setting up the bolster position more efficiently after the maintenance or inspection.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.